In general, a parking brake, which is used to temporarily park a vehicle or park a vehicle on an inclined place such as a hill, applies pressure to a wheel by using cables pulled by a hand unlike a brake that applies pressure to a wheel by using oil pressure generated by a general pedal. The parking brake is operated by a parking lever provided near a driver's seat.
The parking brake includes a parking lever, a parking brake cable, and an equalizer. The parking lever is operated by a hand. The parking brake cables are pulled or loosened by a latch assembly (not shown) operated by a release knob, which is provided in the lever and releases the brake. The equalizer is provided between left and right cables connected to left and right rear wheels, and uniformly distributes an operation force.
The above-mentioned parking brake is generally locked by a strong contact force generated by pressing pads against a drum, which is provided in the wheel, with an operation force of the parking brake.
Further, a manner using a caliper for performing braking with a disk plate positioned between pads is also used instead of a manner pressing the pads against the drum. The caliper, which forms the parking brake and applies a braking force to the disk plate, is generally called a BIR caliper (Ball-In-Ramp Caliper).
As a parking brake using the BIR caliper is operated, an axial force is generated in the BIR caliper by a parking cable. That is, when a pulling force of the parking cable is changed into torque of a ramp and the positions of balls provided in the BIR caliper are changed, an increased axial force is generated at an opposite ramp due to the movement of the balls and pads are pressed against the disk plate due to the axial force. As a result, a parking braking force is generated.
However, the BIR caliper generates a parking braking force by using the ramp that generates an axial force along a movement trajectory of the ball according to the rotation of the ramp to which a parking braking is input. Accordingly, the BIR caliper should generate a parking braking force that is smaller than a braking force used to brake a driving car but is enough to restrict to the movement of the vehicle. For this reason, during parking braking, large initial input is needed to operate the BIR caliper.
A driver's operation unit, that is, a parking lever should be operated to have a large angle to increase the initial input used to operate the BIR caliper during parking braking. For this reason, there is a problem in that a driver's operation force is increased to perform parking braking.